Power actuator



Juy 8, B936. C, s, BRAGG ET AL POWER AGTUATOR 1925 2 Sheets-Sheet l Original Filed Nov. 5

INVENTOR;

HEY ,f 93@ C. s. BRAGG ET AL ,77,194

POWER ACTUATOR Original Filed Nov. 5. 1925 2 Sheets-Sheet 2 proper proportions Patented July 8, 1930 UNITED STATES PATENT OFFICE CALEB S. BRAGG, OF PALM BEACH, FLORIDA, AND

vieron w. KLIEsaA'rH, or roar WASHINGTON, NEW YORK, ASSIGNORS TO BRAGG-KLIESRATH CORPORATION, OF LONG ISLAND CITY, NEW YORK, A CORPORATION OF NEW YORK POWER ACTUATOR Application led November 5,

Our invention consists in the novel features hereinafter described, reference being had to the accompanying drawings which show one embodiment of our invention, selected byus for purposes of illustration, and the said .i11- vention is fully disclosed in the following description and claims.

Our present invention is an improved power actuator especially advantageous for oper ating brake mechanism of automotive vehicles, and conveniently operated from the intake manifold, or suction passage, of the internal combustion' engine which propels the vehicle, although it may be employed for other purposes, as for operating steering or other mechanism for automotive vehicles Voperating on land, on or in water or in the air. In operating a power actuator requiring a very considerable amount of power, it is desirable to keep the size or diameter of the actuator cylinder or cylinders as small as possible to economize space and weight, and it is highly important where such actuators are operated by atmospheric pressure working against a partial vacuum obtained by a connection with the'suction passage of the internal combustion engine, that the smallest quantities of air possible be withdrawn fromthe actuator and discharged into the said suction passage, in order that the of air and fuel in the mixture passing to the -engine shall not be materially altered. The proper operation of an internal combustion engine requires the supply of explosive charges of predetermined proportions of air and fuel, regulated as to quantity by the usual throttle valve, and the admission of large quantities of air into the suction passage is naturally attended by the danger of alteringthe proportions of air and fuel in the mixture to s uch an extent as to stall the engine, if idling, or otherwise interfering with its proper operation.

In carrying out our present invention, we propose to employ a plurality of actuator cylinders andpistons, each cylinder being closed at both ends and one'cylinder only being provided with reversing valve mechanism,constructed and arranged so as to maintain a -rariied condition on both faces of 1925, Serial No. 66,960. Renewed January 17, 1928.

the piston in each cylinder when the pistons are in the oif or normal position, and to admit atmospheric air on one side or face of each piston to effect the power stroke of each, as for example, the application of brake mechanism, while on the return stroke, the reversing valve mechanism admits atmospheric air on the opposite side or face of one piston only, and maintains the other piston or pistons immersed in vacuum. By this construction, portions of the brake mechanism of an automotive vehicle may be operated by separate unconnected pistons under the control of one valve mechanism, and the brake mechanism of a trailer may also be controlled by the valved actuator located on the main vehicle, which operates the brakes thereof, and the diameters of the cylinders and pistons can be kept down while providing the necessary power, for example to apply the brakes of large trucks, buses, automobiles, or othervehicles with trailers and the like,without interfering with the operation of the engine supplying the motive power to the vehicle and the suction for operating the power actuators. On theA power stroke of the pistons when so arranged, practically no air will be discharged into the intake manifold ofthe engine, and while on the return stroke the air admitted to both cylinders for .the power stroke will be exhausted .anddischarged into the manifold. After the pistons are returned to the off or normal position, the air admitted to one cylinder only (or to less than all of the cylinders if more than two are employed) will be exhausted, thus reducing very considerably the quantity of air which would otherwise be admitted to the manifold, and assisting in avoiding the danger of interfering with the carburetion and stalling of the motor if idling. The admission of atmospheric air to a single cylinder would ordinarily be more than ample to insure the release of the brakes, and the return of the piston or pistons of the other cylinder or cylinders to the off or normal position, which pistons are immersed in vacuum, will be readily accomplished by the load of the brake shoes or brake bands or by to the power exerted 'by the actuator, and

We are able to dispense with a retracting spring in conjunction with the mam f or valved actuator, which is objectionable, as

it increases the load upon the actuator and increases the load which would have to be overcome by the operator in applying the brakes connected with the main actuator piston by physical force. The use of aI retracting spring in'connection with the auxiliary actuator is not so objectionable, as the piston thereof is not operated by the physical power of the operator at any time, and such spring does not add to the resistance which he must overcome, and the more important effect is obtained of economizing in the amount of air delivered to the intake manifold.

Referring to the accompanying drawings,

Fig. 1 represents diagrammatically an installation of our improved power actuator in connection with an automotive vehicle and a trailer propelled thereby.

Fig. 2 is an enlarged sectional view of the main or valved power actuator, preferably installed upon the main automotive vehicle,

Fig. 3 is a similar view of the valveless actuator cylinder and piston which may be installed upon a trailer or upon the main vehicle for actuating certain of the brake mechanisms thereof.

Fig. 4 is an enlarged detail sectional view of the reversing valve mechanism of the valved actuator.

In the drawings we have shown an embodiment of our invention, including a main actuator, herein shown as located on an automotive vehicle and controlling all of the brake mechanisms thereof, and an auxiliary actuator mounted on a trailing vehicle, propelled by the main vehicle, and operating all of the brake mechanisms of the trailer, the main actuator being provided with reversing valve mechanism for controlling both actuators,.as hereinafter described, but it is to be understood that the auxiliary actuator (or an additional auxiliary actuator) may also be located on the main vehicle vand used to apply the same brake mechanism to which the main actuator piston is connected, or the main and auxiliary actuators may be employed to operate different brake mechanisms of the same or connected vehicles.

As shown in Figures 2 and 4, the main actuator comprises a cylinder, 1, provided with heads, 2-2,and a double acting piston, 3, to the hub of which are attached, in this instance, oppositely extending hollow piston rods, 4, 5, projecting through suitable stuffing boxes, in the heads, 2-2. The hub, 10, of the piston, is provided with reversing valve mechanism illustrated in detail in Fig. 4, although the specific form of this mechanism does not form part of our present invention. In this instance, thc hub, 10, is provided with valve chambers, 11 and 12, each provided with oppositely disposed conical valve seats, indicated at 13, 14, 15 and 16, to receive conical valves, 40, 41, 42 and 43. Between the valve chambers is located a suction chamber, 17, with which the valve chambers communicate by openings controlled by the suction valves, 41 and 42. Atmospheric air, or other higher pressure iiuid, may be admitted to the valve chamber, 11, through apertures, 4a, at the outer end of the piston rod, 4, under the control of the valve, 40, and to the valve chamber12, through an aperture, 5a, in the piston rod, 5, under the control of valve, 43; 20 represents a valve actuating sleeve which extends through the hollow piston rods, 4 and 5, the piston hub, and the valves, 40, 41, 42 and 43. The valves are provided with yielding retracting means tending to seat them and with means for sealing the apertures in the valves through' which the sleeve, 20, passes. We prefer to make the valves of molded rubber and to construct them s0 that they tit air-tightly around the sleeve, while permitting the sleeve to move through the central apertures in the valves. We also prefer to employ annular spring retracting devices, indicated at 50, losel)7 engaging the sleeve, 20, and interposed between the oppositely disposed valves, 40, 41, and 42, 43. The valve actuating sleeve, 20, is provided with collars, 40a, 41a, 42a and 43a, secured thereto by spring rings or otherwise, for engaging the respective valves in a direction to open them.. The collars, 41u and 42a, are so arranged as to hold both vaves, 41 and 42, off their seats when the piston is in oif or normal position, thereby establishing communcation between the suction chamber, 17, and the cylinder, on both faces of the piston, through valve chambers 11 and 12, and ports, 34 and 35, connecting the chambers, respectively, to the cylinder, the ports, 34, being located on one face of the piston, and the ports, 35, being located on the other face of the piston. The valve actuating sleeve, 20, is provided with apertures, 21, communicating with the suction chamber, 17, and adjacent to said apertures the sleevev is provided with a' plug or partition, 22. The end of the sleeve, 20, communicating with the apertures, 21, is connected outside of the cylinder with a suitable source of suction, as the intake manifold of the internal combustion engine, which propels the main vehicle, by a suction pipe, 62, a portion of which is flexible, date the longitudinal movement of the sleeve, and said sleeve is also provided with means, as a perforated lug, 23, for connecting it with sov to accommo- 6, of the cap,

clearly shown in Fig.

an operator operated part. In this instance we have shown it in Fig. l connected by a link, 85, with a pivoted foot lever, 88, provided with a rctracting spring, 89, and a stop,

88, which in this instance arrests the returnmovement of the sleeve in such position as to hold the valves, 41 and 42 in slighty open position, when the piston is in its retracte position, as shown in Fig. 2.

The auxiliary actuator comprises a cylinder, 101, closed at each end by heads, 102, and provided with a piston, 103. The auxiliary piston is preferably provided with a hollow hub, 110, to which are secured hollow piston rods, 104, 105, extending through stutting boxes, in the opposite heads. Referring again to Fig. 2, it will be noted that there is a certain amount of lost motion between the valve actuating sleeve, 20, and the main actuator piston, suicient to operate the reversing valve mechanism, and it is desirable to limit this lost motion in order that the main actuator piston and the parts connected therewith, as the brake mechanism of the .main

. vehicle or a portion of the brake mechanism thereof, as the case may be, will be positively actuated by the operator operated part on failure of power, or to enable the operator to add his physical power to that exerted by the main actuator, if desired. -It is convenient to accomplish this by providing the valve actuating sleeve, 20, with a collar, 24, within a cap, 6, on the end of the main actuator-piston rod, 5, and located between the outer wall, and an internal flange, 6b, as

The auxiliary actuator cylinder is also connected with the intake Amanifold or suction pipe, 62, in such manner that its piston, 103, is also submerged in vacuum, when the part-s are in the off position. We prefer to connect the auxiliary cylinder, 101, at the rear of the piston when in retracted position (at the left in Fig. 3), with the corresponding portion of the main cylinder, by a pipe or passage, 107, and to connect the opposite end of the auxiliary cylinder (at the right in Fig. 3) directly with-the suction pipe, 62, by a pipe or passage, 108, independently of the reversing valve mechanism. By this construction it will be noted that while the reversing valve mechanism can admit atmospheric air or higher pressure fluid in rear of the main and also the auxiliary piston, to produce a power stroke of both pistons, and also admit the higher pressure fluid on the forward side of the main piston to produce the return movement of the same to normal position, it cannot admit the higher pressure fluid to the auxiliary cylinder on the forward side of the auxiliary piston, as that portion of the auxiliary cylinder is always connected directly with the suction pipe. Consequently, no air will be withdrawn from the auxiliary actuator cylinder on the forward side thereof after rarefication is once effected therein, and

4there is therefore that much less air to be delivered to the intake manifold of the engine, and the danger of linterfering with the operation of the engine or stalling it if idling, is correspondingly reduced. The piston rod, 5, of the main actuator, and the piston rod, 105, of the Vauxiliary actuator, are connected to parts to be operated, as brake mechanism of an automotive vehicle. They may be connected to the same brake mechanism or they may be connected to different brake mechanisms of the same vehicle, or one may be connected to the brake mechanism of one vehicle and the other may be connected with the brake mechanism of another vehicle, as a trailer, ropelled by the main vehicle, so that the bra es of both vehicles will be simultaneously applied and released, as indicated in Fig. 1. Obviously, the piston rods may be connected to the brake mechanisms which they lare intended to operate, by any suitable means, and the actuator may be employed with any usual or preferred types of brake mechanism. .i

In the accompanying drawings we have illustrated an installation in which the piston rods of the actuators are so connected as to operate hydraulic brake mechanisms, but we do not limit our invention to this arrangement, as obviously, mechanical connections of usual or preferred construction could be employed. In Fig. 1, in which the main actuator is connected operatively with a fourwheel brake mechanism for the main vehicle, the piston rod, 5, is connected to a main hydraulic pist-on, 203, working in a hydraulic cylinder, 201, which is conveniently supported by screwing it on the hub of the adjacent head, 2, of the main actuator, and the main hydraulic cylinder, 201, is connected by piping, indicated at 210, with a plurality of brake applying cylinders, 211, each of which is provided with a piston, 212,` shown in dotted lines in Fig. 1, connected in any usual or desired manner, with brake mechanisms, indicated as a whole at 213, in this instance being the four-wheel brakes of the main vehicle. The main hydraulic cylinder is shown provided with a liquid reservoir, 214, for the noncompressible liquid (oil, for example), employed in the hydraulic system, the reservoir being shown connected with the cylinder, 20.1, by a passage, 215, containing a check valve, 216,- and by a passage, 217, adjacent to the piston when in retracted position, for venting the system. The details of the 'hydraulic system, however, form no part of our present invention, but are covered by a separate application for Letters Patent of the United States, filed by us on August 25, 1925 and given Serial Number 51,300 and they will not be more particularly described nor claimed herein. In this instance, the hydraulic cylinder, 201, is provided with breathing apertures, 218, in rear of the piston, 203,

which communicate with the air inlet aper- Y tures, 5, in the hollow piston rod, 5, of the main actuator, so as to establish communication from the atmosphere to the air inlet valve, 43, around the inner end of the sleeve, 20, and the sleeve, 20, may also be provided with additional apertures, 22, beyond the partition, 22, if desired, to facilitate the admission of air which may also pass longitudinally of the sleeve when the valve, 43, is open.

Theauxiliary actuator cylinder, 101, is in this instance shown in connection with a trailer provided with four wheels and the piston, 105, of the auxiliary actuator, 1s operatively connected with the brake mechanism, in this instance a four-Wheel hydraulic brake system, of the trailer. The piston, 105, is connected to a hydraulic piston, 303, in a hydraulic cylinder, 301, constructed in this instance in all respects similar to the corresponding parts of and pertaining to the hydraulic cylinder, 201, which parts are shown in detail in Fig. 3 and given the same numbers as those in Fig. 2, with the addition of 100, and need not be again speciiically described. The pressure pipe or pipes, 310, are connected with brake applying cylinders, 311, for operating pistons, 312, and applying brake mechanism indicated generally and diagrammatically at 313, and in this instance being a four-wheel hydraulic brake mechanism of any usual kind. Where the auxiliary cylinder is mounted on a trailing vehicle, it is obvious that the pipes, 107 and 108, before referred to, will be provided with iiexible portions indicated at 107a, and 108:L in Fig. 1, from one vehicle to another, for accommodating the relative movement between the two vehicles in passing over the road, without interfering with the conductivity of the piping.

The parts beingconstructed and arranged substantially as described, the operation will be as follows: In the normal or off position, the pistons of the main and auxiliary act-uators are in retracted position, as shown in Figs. 2 and 3, and the valves 41 and 42, Will be held olif their seats as indicated in those figures and in Fig. 4, by the stop, 88a, which arrests the sleeve, 20, just before the piston, 3, comes to rest against the rear end plate of the cylinder, 1. It follows, therefore, that the main actuator cylinder, 1, will be exhausted on both sides of the piston, 3,'through ports, 34 and 35, and the auxiliary actuator cylinder will likewise be exhausted en both sides of the piston by means of the pipes or passages, 107 and 108. To apply the brakes controlled by both cylinders. the operator will move the brake lever forward so as to effect the movement of the valve actuating' sleeve, in the direction of the arrow in Fig. 2, thereby seating the valve 41, and further opening the valve, 42, continuing the connection between the cylinder of the forward side of the piston with the suction chamber (at the right in Fig. 2) and opening the valve, 40, continuing the connection between the cylinder on the forward side of the piston, with the suction chamber (tothe right in Fig. 2) and admitting atmospheric air into the main actuator cylinder, l, in rear of the piston, 3 (that is to the left in Fig. 2) and simultaneously admitting atmospheric air from the main actuator cylinder, l, to the auxiliary cylinder, 101, in rear of the piston, 103, that is (to the left in Fig. 3) through pipe, 107. Both pistons, 3 and 103, will therefore move in the direction of the arrows in Figs. 2 and 3, each operating the hydraulic piston connected therewith (203 andy 303) without admitting any appreciable amount of air from either cylinder' to the intake manifold, and applying the brakes controlled thereby.

As soon as the movement of the valve actuating sleeve stops, a very slight continued movement of the piston, 3, in the same direction, will seat the valve, 40, shutting olf the source of pressure, and holding the load of the applied brakes. lo effect the release and reapplication of the brakes, which is often desirable in descending a longl grade or in traiiic, the operator may release the brakes by slightly relieving his pressure on the brake lever, and permitting the retracting spring, 89, to move the valve actuating rod in a direction opposite that indicated by the arrow in Fig. 2. This etiiects the slight opening of the valve, 41, permit-tin g an immediate equalization of pressure in both actuator cylinders on opposite sides of the piston and permitting the brakes to relieve themselves without admitting air on the forward sides of the actuator pistons, and at the same time connectingboth ends of both cylinders with the suction means, thus withdrawing portions of the air previously admitted in rear of the pistons, 3, and 103, for the application of the brakes. The brakes may be immediately reapplied by moving the brake lever forward again, thus closing the valve, 41, and reopening the valve, 40, and this operation may be repeated as often as desired, without, as a matter of fact, withdrawing any very considerable quantity of air from the cylinder into the manifold, as the movements of the pistons during periods of continued braking, i. e. a partial release and reapplication of the brakes, are so slight, and no air is admitted to either cylinder forward of the piston therein. When it is desired to return the parts to normal or 0H position, the operator removes his foot from the brake lever, permitting the retracting spring to move the valve actuating rod in a direction opposite that of the arrow in Fig. 2. This edects the opening of the valve, 41, to withdraw air previously admitted in rear of the pistons, 3 and 103, for the application piston,

of the brakes, the closing of valve, 42, and the opening of valve, 43. Thev latter admits air (or higher pressure iuid) into c linder, 1, through port or ports, 35, forwar of the piston, 3 (at the right in Fig. 2) but no air is admitted to cylinder, 101, forward of the 103, which becomes immersed in vacuum by means of the pipe, 107, extending to the corresponding portion of the cylinder,

relieving the 1,-and the pipe, 108, which is always connected with the intake manifold or suction means. The piston, 3, is returned to normal position positively, by the air admitted through the valve, 43, carrying with it its hydraulic piston, 203, and thus positively pressure on the brakes connected therewith. The piston, 103, is returned to normal position by entirely inde, pendent means. This may be effected by the load of the brakes connected with its hydraulic piston, 303, but we preferably provide a retracting spring for the piston, 103, in order that it will berestored to normal position positively, and carry with it its hydraulic'piston, 303, to positively relieve the pressure on the brakes operatively connected therewith. In this instance we have shown the hollow piston rod, 104, connected to the piston, 103, provided at its outer en with a collar, 70. Between the said collar and the end of the adjacent c linder head, 102, is provided a' coil spring, 1, surrounding the `piston rod, which is compressed when the piston, 103, moves forward, and it effects the retraction of the piston, 103, and the piston, 303, to their normal positions when the foot lever, is released, as previously described.

The objection to the use of retraction springs generally,

come by the physical force of the operator in case it becomes necessary, through failure of power, to actuate the brakes by his physical force, does not apply to the spring,

f 71, for the reason that in this constructlon the operator,

under such conditions, can only actuate the piston, 3, and ae hydraulic piston, 203', and brakes` operatively connected therewith, and therefore, this spring, 71, for returning the auxiliary piston, does not add anything in the way of resistance to the physical force of the operator, and the actuator cylinder andL plston are made of sufiicient size to overcome the pressure of this retracting p the brakes by power with the desired force. `When the parts come to rest in retracted position, the valve actuating sleeve will be arrested, in -this instance, as shown, by the foot lever engaging the stop, 88a, in such position as to hold both the valves, 42 and 43, cracked'or partially open, thus permitting multaneous equalization of pressures and the withdrawal of the air admitted to said cylinder only, in 'edecting the return stroke o spring and apply v to wit, that they provide additional resistance which must be overwithin the cylinder, l, a s1- the piston, 3. This reduces the amount of air to be exhausted, as none has been admitted to the auxiliary cylinder, 101, the return stroke of the auxiliary piston being effected by other means, and this smaller quantity of air can be distributed into the manifold under the controlof the regulating or restricting means, so as not to lnterfere materially with the operation of the engine.

We therefore obtain by our invention greatly increased power from actuators having cylinders of comparatively small diameter, Without a' corresponding increase in the amount of air to be delivered into the manifold. i We also prefer to place a check valve, 62, in the pipe, 62, between the intake manifold and the cylinders, to maintain within the c linders, during the periods when the thrott e is open, the maximum rarication obtained each time the throttle is closed. We also prefer to provide restricting means for the suction pipe or passage, strictlng valve, 62h, in the suction pipe, 62, adjacent to the intake manifold, in this instance, in order to prevent the air withdrawn from the actuators being delivered into the intake manifold so rapidly as to interfere with the'operation of the engine or to stall d it, if idling.

It will also be understood that in case of failure of power, the operator can apply his physical force to the actuator piston, 3, and hydraulic piston, 203, to apply the brakes connected with the latter, and may, if desired, add his physical force to the force exerted by the piston, 3, when the latter is operating under power, by taking up the lost motion between the collar, 24, attached to the valve` actuating sleeve, 20, and the collars, 6 and 6", attached to the piston rod, 5, so that the actuation of the brake mechanism connected with the main actuator piston may always be et'ected, even should the power fail for any reason.

What we claim and Letters Patent is l. The combination of a main actuator, comprising a cylinder, al double acting piston therein, and means including reversing valve mechanism and connections therefrom to a source of suction and to a source of higher pressure Huid, for establishing difdesire to secure by ferential pressures on opposite faces of the iston, said valve mechanism being constructed to hold said piston in a balanced condition in an interjacent position of said valve mechanism, an auxiliary actuator comprising a cylinder, and a piston therein movable independently of the main actuator piston, the portion of said cylinder on one face of the piston being connected with the corresponding portion of the main actuator cylinder, and the portion of the auxiliary actuator cylinder on the opposite face as for example, a re` of the piston, havf ing an outlet passage independent of said 130 mil to a source f suction, and to a source of higher pressure fluid, for establishing differential pressures on opposite faces of the piston, said valve mechanism being constructed to hold said piston in a'balanced condition in an interj acent position of said valve mechanism, an auxiliary actuator comprising a cylinder and a piston therein movable independently of the main actuator piston, the portion of said cylinder on one face of the piston being connected to the corresponding portion of the main actuator cylinder, and

the portion of the auxiliary actuator cylin- Vder'on the opposite face of the piston` having an outlet passage independent of said reversing valve mechanism,y connected with the source of suction, means for holding the reversing valve mechanism in position to connect the main actuator cylinder on both faces of the piston with the source of suction, when the main piston is in the off or normal position, and means fer effecting' the return stroke of the auxiliary piston Without admitting higher pressure fluid to the auxiliary cylinder, whereby both pistons are normally immerse-d vacuum and higher pressure duid may be admitted to both cylinders on one side of each piston to effect a power strokehand Withdrawn from both cylinders, and may be admitted to the main actuator cylinder only on the reverse face cf the main actuator piston, on the return stroke, to minimize the quantity of higher pressure fluid exhausted by the suction source.

3. The combination of a main actuator, comprising a cylinder, a double acting piston therein, and means including reversing valve mechanism and connections therefrom to a source of suction and to a source of higher pressure fluid, for establishing differential pressures on opposite faces of the piston, said valve mechanism being constructed to hold said piston in abalanced condition in an interjacent position of said valve mechanism, an auxiliary actua-tor comprising a cylinder, and a piston therein, the portion of said cylinder on one face of the piston being connected to the corresponding portion of the main actuator cylinder, and the portion of the auxiliary actuator cylinder on the opposite face of the piston having an outlet 1 passage independent of said reversing valve imode-a mechanism, connected with the source of suction, said pistons being disconnected from each other, independent connections from each piston to parts to be operated thereby, and means for eecting the return stroke of one of said pistons Without admitting air to the cylinder thereof, whereby higher pressure fluid may be admitted to both cylinders to effect the power stroke, and Withdrawn from both cylinders, and may be admitted to one cylinder only to effect the return stroke.

4. The combination of a main actuator, comprising a cylinder, a double acting pis- "ton therein, and means including reversing valve mechanism and connections therefrom to a source of suction, and to a source of higher pressure fluid, for establishing differential pressures on opposite faces of the piston, said valve mechanism being constructed to hold said piston in a balanced condition i-n an interjacent position of said valve mechanism, an auxiliary actuator comprising a cylinder and a piston therein movable independently of the main actuator piston, the portion of said cylinder on one face of the piston being connected to the corresponding yportion of the main actuator cylinder, and

the portion of the auxiliary actuator cylinder on the opposite face of the piston, having an outlet passage independent of said revers` ing valve mechanism, connected With the source of suction, means for holding the reversing valve mechanism in position to conneet the main actuator cylinder on both faces cf the piston With the source of suction, when the main piston is in the ofi77 er normal position, said pistons being independent of each ether, operative connections from each piston to parts to be operated thereby, and means for effecting the return stroke of the auxiliary piston Without admitting higher pressure fluid to the cylinder therefor, Whereby both pistons are normally immersed in vacuum, and higher pressure fluid may be admitted to both cylinders on one side of each piston to effect a power stroke and Withdrawn from both cylinders, and may be admitted to the main cylinder only on the reverse face of the main actuator piston, on the return stroke, to minimize the quantity of higher pressure fluid exhausted by the sue tion source.

5. The combination in an automotive vehicle, provided With an internal combustion engine,` and brake mechanism, of a main actuator comprising a cylinder, a double acting piston therein, and means including reversing valve mechanism, and connections therefrom to a source of suction and to a source of higher pressure fluid for establishing differential pressures on opposite faces of the piston, said valve mechanism being constructed to hold said piston in a balanced condition in an intel-jacent position of said valve mechanism, an auxiliary actuator com- Cil lili) able independently prising a cylinder and a piston therein, movof themain piston, the portion of said auxiliary cylinder on one face of its piston being connected to the corresponding portion of the main actuator cylinder and the portion of the auxiliary actuator on the opposite face of the piston. having an outlet passage independent of said reversing valve mechanism connected with the source of suction, a connection from each piston to brake mechanism, whereby higher pressure iiuid may be admitted to both cylinders .to effect the power stroke and apply the brake mechanism connected with each piston, and withdrawn from both cylinders and may be admitted to the main cylinder only to effectthe return stroke of the main actuator piston and permit the brakes connected with the auxiliary piston' to releasethemselves, to minimize the quantity of-higher pressure iiuid exhausted by the suctionl source.

6. The combination in an automotive vehicle, provided with an internal combustion engine, and brake mechanism, of a main actuator comprising a cylinder. a double acting piston therein` and means includingreversing valve mechanism, and connections therefrom to a source of suction and to a source of higher pressure fluid for establishing differential pressures on opposite faces of the piston, said valve mechanism being constructed to hold said piston in a balanced condition in an interjacent position of said valve mechanism` an auxiliary actuator comprising a cylinder and piston therein, movable independently of the main piston, the portion of said auxiliary cylinder on one face of its piston being connected to the corresponding portion of the main actuator cylinder, and the portion of the auxiliary actuator on the opposite face of lthe piston having an outlet passage independent of said reversing valve mechanism connected with the source of suction, a connection from each piston to brake mechanism, and yielding retracting means forl securingl the return stroke of the auxiliary actuator piston and the release of the brake mechanism connected therewith, whereby higher pressure fluid may be admitted to both cylinders to effect the power stroke and apply the brake mechanism connected with each piston, and withdrawn from both cylinders and may be admitted to the main cylinder only to effect the return stroke of of the main actuator piston and permit the brakes connected with the auxiliary piston to release themselves to minimize the quantity of higher pressure fluid exhausted by the suction source.

7. The combination in an automotive vehicle, provided with an internal combustion engine, and brake mechanism of a main actuator, comprising a cylinder, a double acting piston therein, and reversing valve mechanism, a suction pipe connecting said valve mechanism with the suction passage of the engine, means for admitting higher pressure Huid t-o said valve mechanism, said valve mechanism being constructed to connect the main actuator cylinder with the said suction passage on both sides of the piston when the piston is in off or normal position, an auxiliary valveless actuator, comprising a cylinder, a piston therein, operating independently of the main actuator piston, a tubular connection between one end portion of the main actuator cylinder and the corresponding end portion of the auxiliary actuatorcylinder. a tubular connection from the opposite end of the auxiliary actuator cylinder and said suction passage, independent of said reversing valve mechanism, independent operative connections between each of said pistons and brake mechanism, and retracting means for the brake mechanism connected with the cylinder for effecting the return movement of the auxiliary piston, whereby both' pistons will be immersed in vacua when in the olf position, and whereby on the power stroke to apply the brakes, higher pressure fluid will be admitted to the corresponding faces of both pistons, but on the return stroke higher pressure fluid will be admitted on the opposite face of the main actuator piston only.

8. The combination in an automotive Vehicle, provided with an internal combustion engine, andv brake mechanism, of a main actuator comprising a cylinder, a double acting piston therein, and means including reversing valve mechanism, and connections therefr'om to a source of suction and toa source of higher pressure fluid for establishing differential pressures on opposite faces of the piston, said valve mechanism being constructed to hold said piston in a balanced condition in an interjacent position of saidvalve mechanism, an auxiliary actuator comprising a cylinder and a piston therein, movable independently of the main piston, the portion of said auxiliary cylinder on one face of its piston being connected to the corresponding portion of the main actuator cylinder, and the portion of the auxiliary actuator on of the piston having an outlet passage independent of said reversing valve mechanism connected with the source of suction. a connection from each piston to brake mechanism, a reti-acting spring for restoring the auxiliary piston and the brake mechanism connected therewith, to normal or off position, operator operated means for said reversing valve mechanism, operatively connected with the main actuator piston by means permitting lost motion, to enable the operator to exert his physical power on the main actuator piston and brake mechanism connected therewith in addition to the power of the main actuator or upon failure of power, whereby the exertion of the physical power of the the opposite face operator will not he resisted by said retract ing spring,

- 9. n a brake actuating mechanism, the combination with independently operated brakes, a main actuator including Valve mechanism, controlling differentials of pressure for the operation of said main actuator, operative conn Actions from said main actuator to one set of brakes, an auxiliar actuator in- 10 cluding a piston connected to t e other set of brake mechanisms, a connection from the main actuator to the auxiliary actuator controlled by said valve mechanism for admitting higher pressure to said auxiliary actu- 15 lator" for a power stroke of its piston, and a direct connection from said auxiliary actuator to the source of lower pressure.

10. The structure of claim 9 in whichthe main actuator is provided with a piston norg@ mally submerged in the lower pressure.

l1. In a brake actuating mechanism, the combination with independently operated brakes, a main actuator including valve mechanism, controlling dierentials of pressure for the operation of said main actuator, operative connections from said main actuator to one set of brakes, an auxiliary actuator including a piston connected to the other set of brake mechanisms, a connection from :zo the main actuator to the uxiliary actuator controlled by said valve mechanism for admitting higher pressure to said auxiliary actuator for a power stroke of its piston, a direct connection from said auxiliary actua tor to the source or" lower pressure, and means for holding both pistons submerged in Vacuum when in retracted position.

1Q. En a brake actuating mechanism, the combination with independently operated io brakes, a main actuator including Valve mechanism, controliing dierentials of pres sure for the operation of said main actuator, Operative ponnections from said main actuator to one set of brakes, an auxiliary actu- 45 ator including a piston connected to the other set of brake mechanisms, a connection from the main actuator to the auxiliary actuator controlled by said Valve mechanism for admitting higher pressure to said auxiliary actuator for a power stroke of its piston, a directconnection from said auxiliary actuator to the source of lower pressure, and means acting on thevalves ofthe valve mecha-nism to maintain both pistons submerged in vacuum when in retracted position.

In testimony whereof we aiix our signatures. f

CALEB S. BRAGG. VICTGR W. KLIESRATH. 

